1. Field of the Invention
The present invention relates generally to authentication of a subscriber in a wireless communication system, and more particularly, to authentication during handoffs of the communication signals within the wireless communication system.
2. Description of the Related Art
Many wireless communication systems use authentication to enhance the security of the system. A wireless communication system typically includes many individual subscriber units (ISU) such as hand held telephone or data devices which communicate with a network of satellites or base stations. A gateway with fixed network intelligence, such as a switching station, communicates with the network of satellites. The switching station that the subscriber accesses with the network of satellites may not be a home switching station because the subscriber is roaming. The switching station in which the roaming subscriber uses is therefore considered a visiting switching station. The subscriber will communicate with the visiting switching station, which in turn communicates back to the home switching station via a public switched telephone network (PSTN) or other type of connection such as a satellite link. This communication with the home switching station permits retrieval of account information about the ISU, including authentication, and transmission of billing information about subscriber use.
Authentication of a subscriber unit in a wireless communication system traditionally occurs during the call set up. The fixed network intelligence grants the use of the communication system to the ISU after the requesting ISU satisfies the authentication requirements of the system. Once the authentication process is completed successfully and the call connection is established, the subscriber can utilize any of the satellites or terrestrial base stations within the communication system.
A satellite based wireless communication system typically includes a plurality of satellites, each of which can handoff the communication link with the ISU to another satellite within the system. For example, in a wireless communication system with a plurality of satellites or space vehicles (SVs), the ISU establishes a communication link with an active satellite. The satellites move in orbit such that the signal quality between the ISU and an active satellite diminishes. However, as the satellites orbit, a new satellite will move into proximity with the ISU such that the new satellite can provide improved quality signal transmission. Typically, the ISU will determine which satellite can provide greater signal quality. A handoff of the communication link with the ISU will occur from the satellite losing the signal (losing SV) to the satellite gaining the signal (gaining SV).
As part of known satellite communication systems, authentication does not occur during a satellite handoff. If an ISU gains unauthorized access during the initial call set up, then the unauthorized user can continue to communicate illegally over the system for the duration of the call, even when handoffs are performed and completed. Accordingly, it is desirable to provide a system and technique for authenticating an ISU during handoffs within a satellite or terrestrial based wireless communication system.